Hi Yann, On Mon, Dec 17, 2012 at 3:12 PM, Yann Droneaud <ydroneaud@opteya.com> wrote:
Le lundi 17 décembre 2012 à 12:41 +0530, Ritesh Harjani a écrit :
Hi Everyone,
When this command (at+cfun=1,1) is executed on phone, it does a reboot. I want to know which and how this command calls the kernel level functions. I googled this, but seems like all the data explains only about AT command and not as to how this reboot process is done.
The kernel alone is not responsible of interpreting Hayes commands (AT).
According to ETSI TS 100 916 V7.4.0 (1999-11) Technical Specification Digital cellular telecommunications system (Phase 2+); AT command set for GSM Mobile Equipment (ME) (GSM 07.07 version 7.4.0 Release 1998), Section 8.2 Set phone functionality +CFUN (found through by http://wiki.openmoko.org/wiki/Hardware:AT_Commands ), this command (AT+CFUN=1,1) is one of the command a "baseband" must implement.
And this command is asking for a reboot. So what you describe seems more likely to be a hardware problem.
On Android phones(some of them) there are essentially two processors. The *Application Processor (AP)* where your Android operating system (AOS) and user interface (UI) lives, and the *Baseband/Cellular Processor (BP/CP)* where all the GSM and other high-tech communication magic happens, including the modem we wish to communicate with. Here, AP and BP communicates via UART (serial line), USB, SPI or through shared RAM and/or a combination of these. Therefore there will always be some path directly accessible from the outside that we should be able to use to communicate directly with the BP. So, what I am asking for is not any hardware problem. What I have figured out that, this command (at+cun=1,1) calls for sysrq reset which does a emergency restart. But, I wanted to know the exact path that it follows before calling Sysrq key. Thank you Ritesh
Regards.
-- Yann Droneaud OPTEYA